With the development of the network technique and the appearance of lots of mobile terminals, such as laptops, personal digital assistants (PDA), mobile telephones and mounted devices, an upsurge in the mobile computing is raised. More and more users may access the Internet via the public mobile wireless network by various terminals in any location. To meet the need of the mobile service, a mobile IP technique is introduced in the network layer.
In the Mobile IP technique, a mobile node (MN) may perform the IP communication by using the initial IP address all the time in the movement. Therefore, an upper layer application carried in the IP network layer may be ensured uninterrupted and continuable.
The operation principle of the Mobile IP is that when an MN is connected to its home network, the MN works in the same manner as other fixed nodes. If the MN finds itself moved to a foreign network, the care of address (CoA) on the foreign network is obtained by the stateful or stateless auto-configuration based on the received information announced by the router. Here, the MN owns the home address and the CoA at the same time. The MN registers its CoA to the home agent (HA) by a ‘binding update’ message. If the correspondence node (CN) of the MN does not know the CoA of the MN, the correspondence node sends the data packets to the home network of the MN according to the home address of the MN. The HA of the MN captures these data packets and transfers these data packets to the MN by using a tunnel mechanism according to the current CoA of the MN. The message sent by the MN to the CN is sent to the HA via a reverse tunnel, and is transferred to the CN by the HA. As the data packets between the CN and the MN are both transferred by the HA in that manner, the manner may be called ‘triangle route’ manner.
In the ‘triangle route’ manner, in order to ensure the upper layer application carried in the IP network layer to be uninterrupted and continuable in movement. A plurality of HAs may be set on the home link. In a prior art, when the current active HA is invalid, the switching process of the HA and the MN is as follows.
The MN detects the invalidation of the HA. Specifically, if the MN may not obtain the prefix of the home address from the HA or the MN may not complete the home registration with the HA, the MN detects the invalidation of the HA. In addition, if the MN fails to communicate with the outer CN via the HA, the MN may detect the invalidation of the HA.
The MN sends an HA address request to obtain a redundant HA address when the MN detects the invalidation of the HA. After obtaining the HA address by the MN, the MN sends a home link prefix request to get its own home address. Subsequently, the MN completes the home registration. The MN re-completes the process of the registration and communication with other CNs.
However, all the binding information retained in the invalid HA is lost. The real-time service is interrupted and the MN needs to re-establish the service connection, which costs greatly and consumes a lot of bandwidth.
Another method of the redundant backup for the HA/MAP. The basic scheme is shown as follows.
1. The HA on the same home link completes the election between the active HA/MAP and the standby HA/MAP by the virtual route redundancy protocol (VRRP).
2. When the active HA/MAP performs message interaction with the MN, the active HA/MAP creates a binding request and a binding update message by expanding the VRRP message to complete the backup of the binding database record from the active HA/MAP to the standby MA/MAP.
3. When the active HA/MAP is invalid, as the backup of the binding information is stored in the standby HA/MAP, the service flow (the triangle route) which is performing communication currently is not impacted and the standby HA/MAP may continually transfer the service between the MN and the CN.
The method creates the binding request and the binding update message by the manner of expanding the VRRP message to complete the backup of the binding database record from the active HA/MAP to the standby HA/MAP. The quality of the communication between the MN and the CN may not be ensured because the backup is not performed in real time.
In addition, as the key message of the security association (SA) has no backup (if the interaction is performed by using a dynamic key), when the CoA of the MN changes and needs to be re-registered by the HA, the MN needs to re-perform the key interaction with the new HA because the key negotiated before may not be retained. The process of the binding update of the MN is delayed.